Chelating compound, and method of use of, poly(2-octadecyl-butanedioate) and the corresponding acid, poly(2-octadecyl-butanedioic acid)

ABSTRACT

A Chelating agent comprising a polymer backbone. The polymer backbone has a plurality of carbon atoms. There are two carboxylate groups or carboxylic acid groups per repeating unit being coupled to separate carbon atoms of the backbone.

NEW RULE 1.78 (F) (1) DISCLOSURE

The Applicant has not submitted a related pending or patentednon-provisional application within two months of the filing date of thispresent application. The invention is made by a single inventor, sothere are no other inventors to be disclosed. This application is notunder assignment to any other person or entity at this time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to Poly(2-Octadecyl-Butanedioate) (and thecorresponding acid, Poly(2-Octadecyl Butanedioic Acid)) and moreparticularly pertains to the use of Poly(2-Octadecyl-Butanedioate) andPoly(2-Octadecyl-Butanedioic Acid) as Chelating Compounds. The Method ofUsing Poly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-ButanedioicAcid) for Chelating purposes is described herein.

2. Description of the Prior Art

The use of chelating agents is known in the prior art. Morespecifically, chelating agents previously devised and utilized for thepurpose of binding heavy metals are known to consist basically offamiliar, expected, and obvious structural configurations, and chemicalcompounds, notwithstanding the myriad of designs encompassed by thecrowded prior art which has been developed for the fulfillment ofcountless objectives and requirements.

By way of example, compounds used to remove heavy metals from aqueoussolutions can be classified in to two general categories, heterogeneousand homogeneous. Heterogeneous materials are insoluble in water and arecharacterized by slow binding kinetics and low adsorption capacities.Homogeneous materials are soluble in water, have high binding kineticsand relatively high adsorption capacities. For example, Geckeler K,Lange G, Eberhardt H, Bayer E authored Preparation and Application ofWater-Soluble Polymer-Metal Complexes, found in Pure & Appl. Chem.52:1883-1905 (1980). These authors state that insoluble chelating resinshave considerable disadvantages, such as reaction in heterogeneous phaseand long contact times.

In general, there are three requirements with which polymers aschelating agents should comply; (1) sufficient solubilizing power of theconstitutional repeating unit which provides water-solubility of thepolymer complexes, (2) a great number of functional groups of thecomplexing agent for a high capacity, and (3) a high molecular weightwhich allows an easy separation by usual methods from the metal notbound to the polymer.

Water-solubility is provided by a high content of hydrophilic groups,e.g. amino, hydroxyl, carboxyl, amide and sulfonic acid groups, orhydrophilic units of the polymer backbone (ether or imino groups).

Bhattacharyya D, et al. in U.S. Pat. No. 6,544,418, teaches IERs (ionexchange resins), such as strong acid or weak acid cationic exchangers,have been used extensively to recover heavy metals and/or prepare highquality water. The typical theoretical capacity of these IERs is fivemeq/gram. This capacity is quite low. For Ni(II), a maximum uptake ofonly 0.15 grams of metal per gram of IER is possible. Several specificexamples are given below.

Heterogeneous Separations

Chelating Resins

Park I H and Kim K M. authored Preparation of Chelating ResinsContaining a Pair of Neighboring Carboxylic Acid Groups and theAdsorption Characteristics for Heavy Metal Ions. The article waspublished in Sep Sci and Tech, 40:2963-2986 (2005).

These authors reported adsorptivities of 0-52 mg metal/gram resin fortheir malonic acid polymer. The resins reported herein had absorptivity(mg metal/gram resin), depending upon the carboxylic acid content, of:

-   -   1. Pb(II) 17.71-52.21    -   2. Hg(II) 9.62-40.26    -   3. Cu(II) 20.44-25.73    -   4. Cd(II) 17.19-46.88    -   5. Ni(II) 4.16-10.56    -   6. Co(II) 16.07-31.82    -   7. Cr(III) 0.00-2.25

The above results were obtained only after a very long incubationdefined as 28 hr incubation at 20 degrees C. and a pH of 5.

Bruening, R L, et al., disclosed in International Patent ApplicationNumber PCT/US92/02730 the production of chelating polymers formed frompolyalkylene-polyamine-polycarboxylic acid ligands covalently bondedthrough a spacer group to a silicon atom and further covalently bondedto a solid support.

The above series of polymers is different from that described in thecurrent invention for several reasons.

(1) The carboxylate or carboxylic acid functional groups in the aboveseries are not located on adjacent or nearly adjacent carbon atoms inthe polymer backbone.

(2) The polymer backbone contains amine functionality. The non-bondingelectron pairs located on these nitrogen atoms may contribute to thechelation ability of these polymers, and will contribute to thethree-dimensional conformation of the polymer. Nitrogen atoms are notpresent in the polymer described in the current invention.

(3) The carboxylate or carboxylic acid groups are attached to thepolymer backbone by pendent chains containing at least one carbon atom.The carboxylate or carboxylic acid groups in the polymer described inthe current invention are directly attached to the polymer chain. (Forthe reported importance of pendent chains as described in the literaturesee Yamaguchi, U.S. Pat. No. 6,107,428 below.)

Unlike the prior art, the carboxylate or carboxylic acid groups in thecurrent invention are directly attached to the polymer backbone. Thesecarboxyl groups may be two, three, or four or more carbons away fromeach other on the backbone. This structure allows the backbone topotentially close on itself, forming a transient non-covalently-boundring structure. In this way, the ring potentially determines the size ofthe molecule or ion that it can chelate within that ring. The larger thering, the larger the molecule or ion. More importantly, the use of ringsize to selectively determine the molecule or ion that will be chelatedwill allow the user to decide which molecule or ion it wishes to havechelated, leaving smaller or larger molecules or ions in the solution.

Hydrogels

Katime I. and Rodriguez E., authored Absorption of Metal Ions andSwelling Properties of Poly(Acrylic Acid—Co-Itaconic Acid) Hydrogels inJ. Mactomol. Sci.—Pure Appl. Chem., A38 (5&6), 543-558 (2001).

The above authors investigated the binding properties of insolublehydrogels and found the process to be very slow, as polymer swelling for100-1000 minutes is required prior to metal adsorption. Additionally,the rate is limited by metal diffusion inside the hydrogel andhydrogel-water interfacial area and desorption is slow, requiring 2 daysin a 0.1M sulfuric acid solution.

Ion-Exchange Membrane

Sengupta S, and Sengupta A K. authored Characterizing a New Class ofSorptive/Desorptive Ion Exchange Membranes for Decontamination ofHeavy-Metal-Laden Sludges. Their paper was published in Environ. Sci.Technol. 1993, 27, 2133-2140.

The authors produced selective chelating exchangers physically enmeshedor trapped in thin sheets of highly porous poly(tetrafluoroethylene)(PTFE).

A cation exchanger, having the chemical formula (R—CH₂—N(CH₂COOH)₂),contains nitrogen functionality.

The cation described above is crosslinked with divinylbenzene, making Rthe styrene monomer. The polymer matrix (R) is covalently attached tothe chelating iminoacetate functional group.

In kinetic studies, Pb⁺² concentration went from 210 mg/L to 125 mg/L in450-500 minutes (about 8 hours) indicating that this solid phaseextraction is slow.

Bhattacharyya D, et al., in U.S. Pat. No. 6,544,418, described a methodto prepare and regenerate a composite polymer and silica-based membrane.The researchers attached a polyamino acid to the silica-based membraneby reacting a terminal amine group of the polyamino acid with one of theepoxide groups on the membrane.

Capacity of these membranes in g Pb/g resin are as follows:

poly-L-aspartic acid=0.12;

poly-L-glutamic acid=0.30.

These capacity levels are approximately 10 times conventionalion-exchange/chelation sorbents. The authors stated that the polyaminoacid functionalization is critical for this effect. The Incubation timeis about 1-2 hours.

Films

Philipp W H, et al., in U.S. Pat. No. 5,371,110, discloses theproduction of films comprised of a poly(carboxylic acid) supported in awater insoluble polymer matrix poly(vinyl acetal). The polymer is madeby treating a mixture made of poly(vinyl alcohol) and poly(acrylic acid)with a suitable aldehyde and an acid catalyst to cause acetalizationwith some cross-linking. The reaction with the aldehyde (1) locks in thepoly(acrylic acid) so that the poly(carboxylic acid) can no linger beremoved from the polymer by water and (2) makes the film insoluble inwater (by cross-linking). The results are given below:

Initial [Pb]=16.37 ppm,

Final [Pb]=1.44 ppm (91% removal)

24 hour incubation.

Davis H, et al., in U.S. Pat. No. 3,872,001, developed a porous filmcapable of removing heavy metal pollutants from aqueous media. Reactedwith the acid groups in the polymeric film backbone is a chelate (suchas EDTA), capable of forming a complex with the heavy metal pollutantsto be removed from the aqueous media.

The most preferred among the chelating agents is EDTA and this procedureremoved from 55-95% of mercury and cadmium from the solution.

Biosorption

Davis T A, Volesky B, and Mucci A., in Water Research 37 (2003)4311-4330, provide a review of the biochemistry of heavy metalbiosorption by brown algae.

Brown algae biomass is a reliable and predictable way to remove Pb⁺²,Cu⁺², Cd⁺² and Zn⁺² from aqueous solutions. This is due in part to thespecific structural conformations of various polysaccharides in thealgae. Without this specific structural arrangement, binding would notoccur. Specifically, alginic acid or alginate, the salt of alginic acid,is the common name given to the family of linear polysaccharidescontaining 1,4-linked B-D-mannuronic (M) and alpha-L-guluronic (G) acidresidues arranged in a non-regular, blockwise order along the chain. Theresidues typically occur as (-M-)n, (-G-)n and (-MG-)n sequences orblocks, where “n” is an integer. The carboxylic acid dissociationconstants of M and G have been determined as pKa=3.38 and pKa 3.65,respectively, with similar pKa values for the polymers.

Polymannuronic acid is a flat ribbon-like chain, its molecular repeatunit contains two diequitorially linked beta-D mannuronic acid residuesin the chair conformation. In contrast, poly guluronic acid contains twodiaxially linked alpha-L-guluronic acid residues in the chair form whichproduces a rod-like polymer. This key difference in molecularconformation between the two homopolymeric blocks is believed to bechiefly responsible for the variable affinity of alginates for heavymetals.

The higher specificity of polyguluronic acid residues for divalentmetals is explained by its “zigzag” structure which can accommodate theCa⁺² (and other divalent cations) ion more easily. The alginates arethought to adopt an ordered solution network, through inter-chaindimerization of the polyguluronic sequences in the presence of calciumor other divalent cations of similar size. The rod-like shape of thepoly-L-guluronic sections results in an alignment of two chain sectionsyielding an array of coordination sites, with cavities suitable forcalcium and other divalent cations because they are lined with thecarboxylate and other oxygen atoms of G residues. This description isknown as the “egg-box” model.

With alginates, the preferential binding of heavier ions was attributedto stereochemical effects, since larger ions might better fit a bindingsite with two distant functional groups. Additionally, the key tobinding in alginates appears to be the orientation of the oxygen atomswith respect to the —COO— group. In guluronic acid the ring oxygen andthe axial O-1 form a spatially favorable environment with —COO—, andopposed to the equatorial.

Homogeneous Separations

Water Soluble Polymers

Rivas B. L. and Pereira E. authored Functional Water Soluble Polymerswith Ability to Bind Metal Ions, publishing their work in Macromol.Symp. 2004, 216, 65-76. Rivas B L. and Schiappacasse L N. authoredPoly(acrylic acid-co-vinylsulfonic acid): Synthesis, Characterization,and Properties as Polychelatogen, publishing their work in J. Appl PolymSci, 88: 1698-1704 (2003).

Water-soluble polymers (WSP) containing ligands at the main or sidechains have been investigated for the removal of metal ions in thehomogeneous phase. These chelating polymers are termed polychelatogens.The authors state that among the most important requirements fortechnological aspects of these polymers are their high solubility inwater, easy and cheap route of synthesis, and adequate molecular weightand molecular weight distribution, chemical stability, high affinity forone or more metal ions, and the selectivity for the metal ion ofinterest.

Also taught is that polyelectrolytes may be distinguished from chelatingpolymers. The former have charged groups, or easily ionizable groups inaqueous solution, while the latter bears functional groups with theability to form coordination bonds.

Membrane filtration processes can be successfully used for theseparation of inorganic species and for their enrichment from dilutesolutions with the aid of a water-soluble polymer. This technique iscalled the liquid-phase polymer based retention, or “LPR” technique.

The main features of a liquid-phase polymer-based retention system are amembrane filtration, reservoir and a pressure source, such as a nitrogenbottle.

Another separation technique involves the removal of metal ions fromaqueous solutions by means of complexation with a water-soluble polymerfollowed by ultrafiltration (UF).

The kinetics of chelation may be time sensitive and require severalhours, up to “overnight”, depending upon the characteristics of thewater-soluble polymer.

These water-soluble polymers form the most stable complexes at pH=5,retaining between 70-75% of Cu(II), Cd(II), Co(II), Ni(II), Zn(II), andCr(III).

At high ionic strength (0.1M NaNO₃), for both Ni(II) and Cu(II), thepolychelatogens show a low retention capacity (<10%). This can beexplained by the shielding effect of the single electrolyte (in excess)on the charge of the polyion. By decreasing the single electrolyteconcentration (0.01M NaNO₃), the behavior changes sharply (45-90%retention depending upon the ion).

Smith, et al., in U.S. Pat. No. 5,766,478, reported a water solublepolymer capable of binding with the target metal, where a polymer metalcomplex is formed and separated by ultrafiltration.

All polymers thus formed contained nitrogen functional groups or werecrown ether derivatives. These polymers demonstrated a 30 minuteincubation time.

The Limitations of Carboxylate and Carboxylic Acid Chelating Groups, asDescribed in the Literature

Bhattacharyya D, et al. in U.S. Pat. No. 6,544,418, indicate that thepolyamino group is a better chelator than the poly carboxylic acidgroup.

Various sorbents/ion exchange materials are available for metal ionsequestration. Unfortunately, however, all of these suffer from thedisadvantage that they possess at most two or three functional groupscapable of ion interaction per attachment site.

Capacity of these membranes in g Pb/g resin are as follows:

poly-L-aspartic acid=0.12;

poly-L-glutamic acid=0.30.

These capacities are approximately 10 times conventionalion-exchange/chelation sorbents. Authors state that the polyamino acidfunctionalization is critical for this effect.

Rivas B L, Pooley S A, Soto M, Aturana H A, Geckeler K E authoredPoly(N,N′-dimethylacrylamide-co-acrylic acid): Synthesis,Characterization, and Application for the Removal and Separation ofInorganic Ions in Aqueous Solution, published in J. Appl Polym Sci 67:93-100 (1998)

The authors indicate that the polyamino group is a better chelator thanthe polycarboxylic acid group, in that incorporation of amidefunctionality into a soluble poly carboxylic acid improved ion retentionto 88-90% (from 60-70%) for all of the above ions except for Pb(II),which stayed at 50%.

W. F. McDonald, in U.S. Pat. No. 6,495,657, disclosed that polyamidesare preferred over polycarboxylic acids for the binding of heavy metals.Polyamides are effective heavy metal catalysts because of thetwo-dimensional structure of the backbone. Amides are known to exist ina partial double bond configuration, thereby making the structure of thepolymer backbone a series of two-dimensional planes with limitedrotation between them. This structural configuration is said to enhancebinding and utility. Furthermore, the patentee states that varying theamine used to form the amide can further alter the utility and bindingcharacteristics of the polymer. In the current invention, the absence ofnitrogen in the backbone prevents the formation of double bonds. All ofthe carbon bonds in the polymer backbone are able to freely rotate. Theprior art above teaches that limiting conformations enhances binding andutility. In the current invention, increasing conformations is shown toenhance binding and utility.

Yamaguchi, in U.S. Pat. No. 6,107,428, discloses that carboxylic acidgroups must have free rotation and not be inhibited by the polymerbackbone in order to be effective chelators. Thus, these authors teachthat the carboxylic acid group(s) can not be directly bonded to thepolymer backbone.

In the polymers based on carboxylic acids produced by polymerizing amonomer of maleic acid or acrylic acid, a carboxyl group bonds directlyto the main chain, and for this reason, the main chain inhibits freerotation of the carboxyl group. Thus, such polymers based on carboxylicacids render unsatisfactory ability in capturing metal ions, especiallyheavy metal ions. The authors found a polymer having the desiredstructure that is soluble in water and has a high ability to captureheavy metal ions. The monomer has a molecular structure having aplurality of carboxyl groups bonded away from the double bond.Accordingly, the polymer has a molecular structure including a pluralityof carboxyl groups which are not directly bonded to the main chain, andfor this reason, free rotation of carboxyl groups is not inhibited bythe main chain. Thus, the polymer is soluble in water and compared withconventional chelating agents, renders an excellent dispersing effect oninorganic particles and a high ability to capture heavy metal ions.

Park I H. and Kim K M. authored Preparation of Chelating ResinsContaining a Pair of Neighboring Carboxylic Acid Groups and theAdsorption Characteristics for Heavy Metal Ions, published in Sep Sciand Tech, 40:2963-2986 (2005). Authors state that better performance isobtained when the carboxylic acid groups are not directly bonded to thepolymer backbone. In this study, two different kinds of short/longmalonic acid pendant groups were added to a chelating polymer backbonein order to optimize the absorptivity toward heavy metals. The authorsprepared chelating resins containing a pair of carboxylic acid groups.In all cases, these were separated by a benzene ring and two methylenegroups or two methylene groups from the polymer backbone. Additionally,both carboxylic acids were attached to the same carbon. The resins withspacer units among pendant chelating groups were more accessible for theadsorption of heavy metal ions than those without spacers, and theintervals between a pair of neighboring chelating groups had been alsocontrolled for the effective adsorption of heavy metal ions. Theadsorption capacities of chelating resins containing carboxylic acidgroups toward heavy metal ions are generally low. The authors reportoptimal adsorption capacities of 18-52 mg/g for their poly carboxylicacids. This is significantly less than the 290 mg/g observed for theinvented polymer.

Davis T A. Volesky B. and Mucci A. authored A Review of the Biochemistryof Heavy Metal Biosorption by Brown Algae, published in Water Research37 (2003) 4311-4330. The authors state that the three-dimensionalconformation of the chelator is important. The authors also state thatfunctional groups responsible for the chelation should preferably bedistant from each other. The higher specificity of polyguluronic acidresidues for divalent metals is explained by its “zigzag” structurewhich can accommodate the Ca⁺² (and other divalent cations) ion moreeasily. The alginates are thought to adopt an ordered solution network,through inter-chain dimerization of the polyguluronic sequences in thepresence of calcium or other divalent cations of similar size. Therod-like shape of the poly-L-guluronic sections results in an alignmentof two chain sections yielding an array of coordination sites, withcavities suitable for calcium and other divalent cations because theyare lined with the carboxylate and other oxygen atoms of G residues.This description is known as the “egg-box” model. With alginates, thepreferential binding of heavier ions was attributed to stereochemicaleffects, since larger ions might better fit a binding site with twodistant functional groups.

Park I -H. Rhee, J. M., and Jung, Y. S. authored Synthesis and HeavyMetal Ion Adsorptivity of Macroreticular Chelating Resins ContainingPhosphono and Carboxylic Acid Groups, published in Die AngewandteMakromolekulare Chemie (1999) 27-34. The authors state that theadsorption ability of chelating resins containing only carboxylic acidgroups toward heavy metals was very low. As a result, various improvedresins containing dithiocarbamates, aminomethyl phosphoric acid groups,amidooximes, imidazoles, mercaptoamines, diphosphonates, and phosphonogroups have been prepared. Adsorption capacities for these improvedresins were still very low, only averaging about 2 mg/g resin. (Bycomparison, the polymer described in this invention had adsorptioncapacities 150 times greater.)

In summary, the characteristics of this polymer are not predicted by theliterature and, as such, the use of the polymer to carry out chelationin the manner described, is unexpected, and constitutes a new andunexpected use for the polymer. Contrary to the literature that teachesthat this polymer should not work in the manner shown empirically, ithas been demonstrated that the polymer, as herein described, functionsin a new, unanticipated manner.

While these compounds disclosed in the prior art fulfill theirrespective, particular objectives and requirements, the aforementionedpatents and prior art do not describe the Chelating Compounds, and theMethod of Use of Poly(2-Octadecyl-Butanedioate) andPoly(2-Octadecyl-Butanedioic Acid) that allows the use of re-usablecompounds for binding and removing heavy metals from a solution.

In this respect, the Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)according to the present invention substantially departs from theconventional concepts and compounds described in the prior art, and indoing so provides compounds primarily developed for the purpose ofproviding re-usable compounds for binding and removing heavy metals froma solution.

Therefore, it can be appreciated that there exists a continuing need fornew and improved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)which can be used in a re-usable fashion for binding and removing heavymetals from a solution. In this regard, the present inventionsubstantially fulfills this need.

SUMMARY OF THE INVENTION

Poly(2-octadecyl-butanedioate) and Poly(2-octadecyl-butane-dioic acid),prepared from polyanhydride PA-18 or other preparative means as would beevident to those skilled in the art, possess novel heavy metaladsorption characteristics. The adsorption capacity of this waterinsoluble polymer for lead (II) was substantially higher than otherheterogeneous adsorbants and is equivalent to those obtained withhomogeneous sorbants. Essential characteristics/benefits are summarizedbelow.

First, the ease of separation of polymer from aqueous media (gravityfiltration) becomes readily apparent, in that heterogeneous separationavoids the use of high pressure ultrafiltration associated with theseparation of aqueous ion solutions and homogeneous sorbents. Also,extremely rapid adsorption of heavy metal ions occurs. Chelationkenetics result in a significantly faster adsorption, and adsorptioncapacity is significantly greater than that observed with otherheterogeneous sorbents. The disclosed compounds have a highly efficientcapacity for metal ions per unit weight of polymer. Adsorption capacityis similar to homogeneous sorbents. A sodium or potassium carboxylateform of chelation groups provides for a relatively large pH range forseparations. Most sorbents release hydrogen ions upon metal chelation,constantly altering the pH of the solution. This tends to limit both thekinetics (speed) of the sorption reaction and the capacity of thesorbant. Chelation is not altered by high sodium ion concentration. Thecompound can be used in applications involving brine solutions, seawater, and urine. Many sorbants can not be used under solutions having ahigh sodium ion content. Heavy metal chelation can be accomplished insolutions with high calcium ion concentrations. The disclosed compoundcan be used in applications involving hard water. Because of the lowerhydration energy associated with the calcium ion, when compared to heavymetals, almost all other sorbents preferentially bind calcium ions. Thislimits both the capacity and the utility of these sorbents.

All biosorbents suffer from lot-to-lot chemical variability and lack ofwidespread distribution, and procedures that affix polymers to insolublesupports are subject to significant variability. This impacts bothpolymer performance and production costs. This variability is absent inthe current invention.

Lastly, the invented polymers are able to bind +1, +2, and +3 ions. Thisis advantageous, and unexpected, in that most polymers bind metalshaving only one or two different oxidation states.

Essential Characteristics of Polymers

The polymers, as herein described, contain numerous sodium (orpotassium) carboxylate groups or carboxylic acid groups directly boundto the polymer backbone that provide the hydrophilic heavy metal bindingcharacteristics. The polymers contain a water insoluble hydrophobicaliphatic polymer backbone. The lack of solubility of the polymers inwater facilitates the ease of separation from aqueous solution. Thepolymers provide specific, selective, and fast complexation of heavy andother metal ions as well as demonstrating reusability of the chelatingpolymeric ligands.

Comparison of Adsorption Capacities

The absorption capacities of various absorbents is given in the tablebelow:

Adsorption Homegeneous/ capacity Adsorbent Heterogeneous (mg g⁻¹)Reference These polymers Heterogeneous 290 — Banana Stem Heterogeneous91.74 12 Tin Oxide Gel Heterogeneous 16.3 7 Sporopollenin Heterogeneous8.52 22 XAD-4 Heterogeneous 12.2 10 Copolymer Resin MacroreticularHeterogeneous 2.05 23 Resins Sargassum sp. Heterogeneous 244 5Polyethyleneimine Homogeneous 120-470 24

The polymers, herein described, have several potential uses that arebeneficial. The polymers may be used for purification of drinking water,for treatment or isolation of hazardous waste, and for purification ofgroundwater. The polymers may also be used as a treatment of industrialdischarge prior to release into the environment, or use as bindingagents for paints to metal surfaces. The polymers may have use aschelating drugs to treat heavy metal/metal toxicity, and in miningoperations to increase the isolation yield of metals found in lowconcentration.

In view of the foregoing disadvantages inherent in the known types ofchelating agents now present in the prior art, the present inventionprovides improved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid).As such, the general purpose of the present invention, which will bedescribed subsequently in greater detail, is to provide a new andimproved Chelating Compound, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)and a method which has all the advantages of the prior art and none ofthe disadvantages.

To attain this, the present invention essentially comprises a Chelatingagent comprising a polymer backbone. The backbone is a water insoluble,hydrophobic, aliphatic polymer structure. There are two sodiumcarboxylate groups or carboxylic acid groups per repeating unit that aredirectly bound to the polymer backbone.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject matter of the claims attached.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of descriptions and should not beregarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other formulations, and methods for carrying outthe several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentformulations insofar as they do not depart from the spirit and scope ofthe present invention.

It is therefore an object of the present invention to provide new andimproved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)which has all of the advantages of the prior art chelating agents andnone of the disadvantages.

It is another object of the present invention to provide new andimproved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)which may be easily and efficiently manufactured and marketed.

It is further object of the present invention to provide new andimproved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)which is easily reproduced.

An even further object of the present invention is to provide new andimproved Chelating Compounds, and Method of Use ofPoly(2-Octadecyl-Butanedioate) and Poly(2-Octadecyl-Butanedioic Acid)which is susceptible of a low cost of manufacture with regard to bothmaterials and labor, and which accordingly is then susceptible of lowprices of sale to the consuming public, thereby making such ChelatingCompounds, and Method of Use of Poly(2-Octadecyl-Butanedioate) andPoly(2-Octadecyl-Butanedioic Acid) economically available to the buyingpublic.

Even still another object of the present invention is to provideChelating Compounds, and Method of Use of Poly(2-Octadecyl-Butanedioate)and Poly(2-Octadecyl-Butanedioic Acid) for the use of a re-usablecompound for binding and removing heavy metals.

Lastly, it is an object of the present invention to provide a new andimproved compound having chelation properties and being able to beregenerated from a chelated solution, allowing re-use of the compound.

These together with other objects of the invention, along with thevarious features of novelty which characterize the invention, arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and the specific objects attained by its uses,reference should be had to the accompanying drawings and descriptivematter in which there is illustrated preferred embodiments of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is a drawing of the compound, showing the pertinent structure andformula.

FIG. 2 is a drawing of Alternate Synthesis of 2-Octadecyl-ButanedioicAcid Analogs.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the drawings, and in particular to FIG. 1 thereof,the preferred embodiment of the new and improved Chelating Compound, andMethod of Use of Poly(2-Octadecyl-Butanedioate, sodium) embodying theprinciples and concepts of the present invention and generallydesignated by the reference numeral 10 will be described. Simplisticallystated, the polymer herein described comprises a plurality of reactivegroups, being carboxylates or carboxylic acid groups. The reactive groupis directly bonded to the carbon backbone.

The initial, or primary component, for the synthesis, is a commonlyavailable, previously described component. The primary component may beprepared as follows:

1. The polycarboxylate is produced from the corresponding polyanhydride.The polyanhydride is produced by a process that is described anddisclosed in U.S. patent application Ser. No. 3,560,456, issued to S. M.Hazen and W. J. Heilman, entitled “Process of forming copolymers ofmaleic anhydride and an aliphatic olefin having from 16 to 18 carbonatoms.”

2. The polycarboxylate is produced from the polyanhydride by thefollowing procedure:

10 grams of the polyanhydride PA-18 are dissolved in 200 ml of 4M NaOHand stirred at 85° C. for 2 hours. The reaction mixture is cooled, thepH adjusted to 6 to 6.5, and vacuum filtered. The solid polymer iswashed with cold analytical grade methanol and dried under vacuum.

There are other methods to produce the polycarboxylate. One method is toproduce the polyester. Subsequent hydrolysis of the polyester wouldproduce the polycarboxylate. These reaction schemes would be obvious tosomeone skilled in the art of organic synthesis or polymer synthesis.

The polycarboxylate has two different binding site populations. Thereactive groups in the repeating unit are two carbons apart, while thereactive groups between the repeating units are four carbons apart.There is direct experimental evidence that these two binding sites havedifferent metal chelation affinities. A number of differentpolycarboxylate polymers may be produced in this way. Polycarboxylatepolymers with reactive groups in the repeating unit 4 carbons apart andbetween the repeating units 6 carbons apart and the correspondingpolymer with 6 (within) and 8 (between), respectively can potentiallyform transient non-convalently bonded ring systems. One can enhancespecificity by tailoring the polymer to fit the size of the metal ionone chooses to chelate. Additionally, the reactive groups must beattached to the backbone and do not have to be attached to adjacentcarbon atoms. It is possible that the polymer chain, being flexible, isable to surround the metal, thereby enhancing chelation.

FIGURES

FIG. 1 shows the form of Poly(2-octadecyl-butanedioic acid) showing twopotential binding sites.

FIG. 1 is the first configuration of the compound.

FIG. 2 shows an Alternate Synthesis of 2-Octadecyl-Butanedioic AcidAnalogs

FIG. 2

-   -   water

Polyester→Polycarboxylate or Polycarboxylic acid

-   -   heat    -   base or acid

FIG. 2 is a second configuration of the compound.

In the above reaction sequence, R in both the reactants and productswould be an aliphatic organic group, such as methyl or ethyl, makingboth the reactants and products esters. The product above could befurther modified by hydrolysis of the ester in either basic or acidicmedia to produce the polycarboxylate or polycarboxylic acid,respectively. In the case of hydrolysis in basic media, if sodiumhydroxide is used, the sodium salt of the polycarboxylate ion would beformed (R═Na⁺). Likewise, if potassium hydroxide is used, the potassiumsalt of the polycarboxylate ion would result (R═K⁺). If one does an acidcatalyzed ester hydrolysis (acid is used in the second reaction above),then the polycarboxylic acid would be produced (R═H).

In these polymers, the carboxylates or carboxylic acid groups areseparated by 0 to 8 carbon atoms.

Procedure for Metal Chelation

Batch sorption experiments were conducted by adding 0.0500 grams of theinsoluble poly(2-octadecyl-butanedioate) or Poly(2-octadecyl-butanedioicacid) to 5.0 ml of a metal ion primary solution. The heterogeneousmixtures form a secondary solution and are agitated at 150 rpm at 22° C.for 15 to 60 minutes. The secondary solution is then gravity filtered.The filtered solution is then free of metal ions. The poly/metal ioncomplex is filtered out in the form of filter cakes containing thepolymer and adsorbed metal ions.

Procedure to Recover Metal Ion from Polymer

A significant advantage of using the herein described polymer for metalchelation is that the polymer is recoverable after binding with themetal within a solution. By recoverable is meant that the polymer canthen be processed and separated from the chelated metal, so that thepolymer can then again be used to chelate a metal containing solution.Such recoverability means less overall cost, and less environmentalimpact, as by separating the polymer from the metal chelated structure,the metal is left, to be processed and recycled. Rather than fillinglandfills, the use of the polymer in the herein described method willallow a once hazardous substance to become a utilitarian substance andis a source of the metal ion.

The process for recovery is quite direct. After filtration, as describedabove, the solid filter cakes containing the polymer and adsorbed metalions are suspended in a dilute acid solution. In the preferredembodiment the dilute acid solution is a 2% nitric acid (HNO₃) solution.The heterogeneous mixtures are stirred at approximately 150 rpm for 30minutes. The sample is then gravity filtered. The filtrate contains theaqueous metal ion and the solid that is removed contains the poly, nolonger in a poly/metal ion complex. The aqueous metal ion solution canthen be treated with a dilute base to precipitate the metal ion out ofsolution, for recycling of the metal ion. The filter cake containing therecovered polymer, or poly, can then be reused in a chelation procedureas a source of poly.

Due to capacities of this and other adsorbents, the ratio of polymer tosolution needs to be fairly constant. The polymer to solution ratio can,however, be varied by a factor of about 200, depending upon the metalion concentration of the solution, and still achieve optimum results.Also variable is the shaking speed. While the preferred embodiment ofthe method uses a shaking speed of 150 revolutions per minute, theshaking speed may be varied from a few revolutions per minute to sixhundred revolutions per minute.

Chelation purposes are uses such as, purification of drinking water,treatment or isolation of hazardous waste, purification of groundwater,the treatment of industrial discharge prior to release into theenvironment, as a binding agent for paints to metal surfaces, as a drugto treat heavy metal/metal toxicity, and as used in mining operations toincrease the isolation yield of metals found in low concentration.

It should be noted that filtration may take place by use of a columnarfiltering apparatus, in which the solution is passed through a filteringmedium that is contained within a column. Filtration, in the context ofthis discussion and the claims will mean suction filtering and columnarfiltering. In addition, any filtering means, that is commonly used andavailable for the filtering of such acids, may be used in this process.

As to the manner of usage and operation of the present invention, thesame should be apparent from the above description. Accordingly, nofurther discussion relating to the manner of usage and operation will beprovided.

With respect to the above description then, it is to be realized thatthe optimum dimensional relationships for the parts of the invention, toinclude variations in size, materials, shape, form, function and mannerof operation, assembly and use, are deemed readily apparent and obviousto one skilled in the art, and all equivalent relationships to thoseillustrated in the drawings and described in the specification areintended to be encompassed by the present invention.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

1. A Chelating agent as shown in FIG. 2 comprising: a polymer backbonehaving a plurality of carbon atoms; and a plurality of reactive groupsbeing coupled to separate carbon atoms of the backbone.
 2. The Chelatingagent as described in claim 1 wherein the reactive group is acarboxylate group.
 3. The Chelating agent as described in claim 1wherein the reactive group is a carboxylic acid group.
 4. The Chelatingagent as described in claim 2 wherein the agent further comprises: thepolymer backbone being a water insoluble, hydrophobic aliphatic polymerbackbone; and the carboxylate groups are directly bound to the carbonatoms in the polymer backbone with said carbon atoms being separated bybetween zero and a plurality of carbon atoms.
 5. The Chelating agent asdescribed in claim 3 wherein the agent further comprises: the polymerbackbone being a water insoluble, hydrophobic aliphatic polymerbackbone; and the carboxylic acid groups are directly bound to thecarbon atoms in the polymer backbone with the carbon atoms beingseparated by between zero and a plurality of carbon atoms.
 6. TheChelating agent as described in claim 1 wherein the agent furthercomprises the reactive groups being directly bound to the carbon atomsin the polymer backbone with the bound-to carbon atoms being separatedby between zero and a plurality of carbon atoms.
 7. The Chelating agentas described in claim 1 wherein the agent further comprises all of theatoms comprising the backbone are Carbon atoms.
 8. A method of using apolymer as shown in FIG. 2 to chelate, the polymer having the formula ofPoly (2-octadecyl-butanedioate, sodium) comprising: providing aninsoluble poly(2-octadecyl-butanedioic acid) also known as “Poly”;providing a metal ion primary solution with the poly and the metal ionprimary solution having a ratio of Poly to metal ion solution; providingthe mixing the Poly with the metal ion solution by agitation to therebyform a secondary solution containing a metal ion and Poly complex;providing the filtration of the secondary solution with the filtrationresulting in a third solution and a filter cake, the filter cakecontaining the metal ion and Poly complex; providing the separation ofthe Poly and the metal ion contained in the filter cake by suspendingthe solid filter cake in a dilute acid solution; providing agitation ofthe dilute acid solution; providing filtering of the dilute acidsolution, the filtering thereby separating the filter cake containingthe Poly and the dilute acid solution containing the metal ion;providing a dilute base and mixing the dilute base with the dilute acidsolution forming a third solution, thereby precipitating the metal ionout of solution; and providing the pouring off of the third solution andleaving the precipitated metal ion for recovery.
 9. A method of using apolymer to chelate, the polymer having the formula of Poly(2-octadecyl-butanedioic acid) comprising: providing an insolublepoly(2-octadecyl-butanedioic acid) also known as “Poly”; providing ametal ion primary solution with the poly and the metal ion primarysolution having a ratio of Poly to metal ion solution; providing themixing the Poly with the metal ion solution by agitation to thereby forma secondary solution containing a metal ion and Poly complex; providingthe filtration of the secondary solution with the filtration resultingin a third solution and a filter cake, the filter cake containing themetal ion and Poly complex; providing the separation of the Poly and themetal ion contained in the filter cake by suspending the solid filtercake in a dilute acid solution; providing agitation of the dilute acidsolution; providing filtering of the dilute acid solution, the filteringthereby separating the filter cake containing the Poly and the diluteacid solution containing the metal ion; providing a dilute base andmixing the dilute base with the dilute acid solution forming a thirdsolution, thereby precipitating the metal ion out of solution; andproviding the pouring off of the third solution and leaving theprecipitated metal ion for recovery.
 10. The method of using a polymerto chelate as described in claim 8 wherein the agitation is carried outat 150 rpm at 22° C. for a time range of between about 15 and 60minutes.
 11. The method of using a polymer to chelate as described inclaim 9 wherein the agitation is carried out at 150 rpm at 22° C. for atime range of between about 15 and 60 minutes.
 12. The method of using apolymer to chelate as described in claim 8 wherein filtration is gravityfiltration.
 13. The method of using a polymer to chelate as described inclaim 9 wherein filtration is gravity filtration.
 14. The method ofusing a polymer to chelate as described in claim 8 wherein the secondarysolution is a heterogeneous mixture.
 15. The method of using a polymerto chelate as described in claim 9 wherein the secondary solution is aheterogeneous mixture.
 16. The method of using a polymer to chelate asdescribed in claim 8 wherein the dilute acid solution is a 2% nitricacid (HNO₃) solution.
 17. The method of using a polymer to chelate asdescribed in claim 9 wherein the dilute acid solution is a 2% nitricacid (HNO₃) solution.
 18. The method of using a polymer to chelate asdescribed in claim 8 wherein the secondary solution is stirred at a rateof between about 3 rpm and 600 rpm for a time period of between about 3minutes and 180 minutes.
 19. The method of using a polymer to chelate asdescribed in claim 9 wherein the secondary solution is stirred at a rateof between about 3 rpm and 600 rpm for a time period of between about 3minutes and 180 minutes.
 20. The method of using a polymer to chelate asdescribed in claim 8 wherein the ratio of polymer to primary solution isbetween about 100:1 and 200:1.
 21. The method of using a polymer tochelate as described in claim 9 wherein the ratio of polymer to primarysolution is between about 100:1 and 200:1.
 22. A chelating agent asdescribed in claim 1 used for chelation purposes.
 23. A Chelating agentas shown in FIG. 2 comprising: a polymer backbone having a plurality ofcarbon atoms; and a plurality of reactive groups being coupled toseparate carbon atoms of the backbone.
 24. The Chelating agent asdescribed in claim 23 wherein the reactive group is a carboxylate group.25. The Chelating agent as described in claim 23 wherein the reactivegroup is a carboxylic acid group.
 26. The Chelating agent as describedin claim 24 wherein the agent further comprises: the polymer backbonebeing a water insoluble, hydrophobic aliphatic polymer backbone; and thecarboxylate groups are directly bound to the carbon atoms in the polymerbackbone with said carbon atoms either adjacent to each other orseparated being separated by between zero and a plurality of carbonatoms.
 27. The Chelating agent as described in claim 25 wherein theagent further comprises: the polymer backbone being a water insoluble,hydrophobic aliphatic polymer backbone; and the carboxylic acid groupsare directly bound to the carbon atoms in the polymer backbone with saidcarbon atoms being separated by between zero and a plurality of carbonatoms.